1. Technical Field
The present invention relates to a test apparatus and a pin electronics card. More particularly, the present invention relates to a test apparatus for testing a device under test such as a semiconductor circuit, and to a pin electronics card for use in the test apparatus.
2. Related Art
A known test apparatus for testing a device under test such as a semiconductor circuit includes a pin electronics card that transmits/receives a signal to/from the device under test. The pin electronics card is provided between the main portion of the test apparatus and the device under test. The pin electronics card inputs a test signal supplied from the test apparatus into the device under test, and receives an output signal from the device under test.
FIG. 4 illustrates an exemplary configuration of a conventional pin electronics card 300. The pin electronics card 300 includes a driver 302, a comparator 304, an FET switch 312, a transmission path 314, and a reference voltage input section 316.
The driver 302 receives a test signal from the main portion of a test apparatus, and inputs the received test signal into a device under test, which is shown as a DUT in FIG. 4. The driver 302 is connected to the device under test through the FET switch 312 and the transmission path 314. The driver 302 includes a level switch 306, an enabling switch 308, and an output resistance 310.
The comparator 304 receives an output signal from the device under test, and compares the signal level of the received output signal with a supplied reference voltage. The comparator 304 is connected to the device under test through the FET switch 312 and the transmission path 314. The reference voltage input section 316 generates a predetermined reference voltage, and inputs the generated reference voltage into the comparator 304.
The FET switch 312 is turned on/off by a supplied gate voltage. The FET switch 312 switches whether to connect the driver 302 and the comparator 304 to the device under test. With the above-described configuration, the pin electronics card 300 exchanges a signal between the main portion of the test apparatus and the device under test. No related references including patent documents have been recognized, and therefore such references are not mentioned here.
While being turned on, the FET switch 312 is represented as an equivalent circuit formed by a resistance that is provided in series between the driver 302 and the device under test, and capacitance components that are respectively provided between the ground potential and the ends of the resistance. The equivalent circuit has a constant RC product, and thus can not realize a low resistance and a low capacitance at the same time.
When having a low on-resistance, the FET switch 312 has a high capacitance while remaining turned on. In this case, the FET switch 312 can not pass a high-frequency signal. This makes it difficult to perform a test by using a high-frequency signal.
For this reason, the on-resistance of the FET switch 312 may be increased to allow a test based on a high-frequency signal. Here, however, it should be noted that the comparator 304 is connected to the device under test via the FET switch 312. Therefore, the on-resistance of the FET switch 312 affects the voltage comparing operation of the comparator 304 when the driver 302 is enabled.
For example, the signal level of the output signal input into the comparator 304 is divided by the output resistance 310 and the on-resistance of the FET switch 312. As the on-resistance of the FET switch 312 increases, the variation of the on-resistance increases. Therefore, a high on-resistance of the FET switch 312 lowers the accuracy of the voltage comparing operation by the comparator 304.
The on-resistance of the FET switch 312 changes in accordance with parameters including the temperature, the source-gate voltage, and the back-gate voltage. Here, the on-resistance of the FET switch 312 changes due to such parameters more significantly when set at a high value. Therefore, a high on-resistance of the FET switch 312 further degrades the accuracy of the voltage comparing operation of the comparator 304.